The following correction appeared in the Guardian's Corrections and clarifications column, Thursday February 8 2007

Lord Kelvedon (Paul Channon) was the last of four members of the Guinness family to represent the Essex constituency of Southend West, not five as we said in the obituary below. President Roosevelt's home at Hyde Park, New York State, where he was Channon's neighbour, was about 75 miles, rather than our 15 miles, north of New York City.

Lord Kelvedon, who has died at the age of 71 after suffering from Alzheimer's disease, was better known as Paul Channon, nine times a Conservative minister under Edward Heath and Margaret Thatcher, and the last of five members of the Guinness family to represent the Essex constituency of Southend West, which he did for 38 years, from 1959 to 1997.

He was an able, intelligent and conscientious minister, a so-called "safe pair of hands", until three blows struck during his two-year tenure as transport secretary (1987-89): the fire at King's Cross underground station in 1987, the 1988 Clapham rail crash and the Lockerbie disaster, when a PanAm airliner was blown out of the sky that December. These events were preceded by personal tragedy when, in 1986, Channon's elder daughter, Olivia, died of a drugs and drink overdose while celebrating the end of her final exams at Christ Church, Oxford. Thatcher dropped Channon from her government in 1989.

Until then, his life had shown that the slogan, "Guinness is good for you" was especially true if you were a Guinness yourself, as Channon was through his mother, Lady Honor Guinness, the elder daughter of the 2nd Earl of Iveagh. His father was Sir Henry "Chips" Channon, the American-born diarist. Although polite and unassuming, he lived his life in a cocoon of wealth derived from the profits of the family breweries funnelled into investments trusts. His share in them was estimated in 1990 at £184m. This enabled him to live a lavish life, with a £3m home in Cheyne Walk, Chelsea, a grade 1 listed country mansion, Kelvedon Hall in Essex, and two villas in Mustique. He was also able to indulge his enthusiasms for opera and fine painting.

On only one occasion did he allow his millionaire's tastes to interfere with politics, an obsession he had developed since childhood. Two days after the Lockerbie disaster, he flew off for a Christmas vacation on Mustique, leaving his junior minister, Michael Portillo, to field biting questions from John Prescott, then shadow transport minister.

Born in London, like many children of the British upper and middle classes, Channon was evacuated to north America during the second world war - in his case to the Astors' home in upstate New York; a neighbour was President Roosevelt, 15 miles north of New York City. He returned to England to find that his mother had run off with a Czech airman. Educated at Lockers Park, Hemel Hempstead, and Eton, he did his national service with the Royal Horse Guards in Cyprus before going on to Christ Church, Oxford, in 1956, where he became president of the university Conservative association.

He was in his final year when his father died, leaving vacant the Tory seat of Southend West, which had been a Guinness fiefdom - tagged "Guinness-on-Sea" - since 1912, when his grandfather, the Hon Rupert Guinness, was first elected. Despite the opposition of Lord Beaverbrook's Daily Express and 129 other Tory aspirants, Paul's grandmother, Lady Iveagh, secured the candidacy for him, declaring: "I think you have done right by backing a colt when you know the stable he was trained in." Channon won the January 1959 byelection by more than 8,000 votes.

With his background, he easily became PPS to a succession of Tory ministers: among them Richard Wood, minister of power (1959-60), and Home Secretary "Rab" Butler (1960-62). A humane man, he was one of the few Conservative MPs to support Sidney Silverman's 1965 bill to end capital punishment; he also opposed the unilateral independence declared by Rhodesia's white minority under Ian Smith.

When Edward Heath formed his government in 1970, he made Channon parliamentary secretary of housing and local government. He was environment under-secretary (1970-72), and from March to September 1972, minister of state for Northern Ireland. During that time, his London home was the venue for a secret meeting between Northern Ireland secretary William Whitelaw and the IRA. Later that year, he became minister of state for housing and construction, staying in post until 1974.

These Heath promotions made Channon anathema to Thatcher after she became Conservative leader in 1975, especially when she had got wind of the 1974 meeting of patrician "wets" who had concluded that she, along with Bernard Braine and Sir Frederick Bennett, were the three least likely people to become leader. "There will be no room in my government for that millionaire," she allegedly told Reginald Maudling.

However, in 1979, when she took power, Thatcher reluctantly named Channon as Lord Soames's deputy at the civil service department - and promoted him when Soames became governor of Southern Rhodesia. Channon became arts minister in 1981, and trade minister two years later. By this time, he had become the longest-serving minister of state.

It was not, however, until 1986 that Channon entered the cabinet as secretary of state for trade and industry, following the resignation of Leon Brittan over the Westland affair. He was soon confronted with the headline-making possibility that General Motors would take over British Leyland and Ford would take over Austin Rover, threats which evaporated

When, the following year, he became transport secretary, Channon continued to show his administrative ability, finishing the M40 motorway, beginning the widening of the M25 and providing British Rail with much-needed additional funds. But his failure to inspire public confidence in the handling of the disasters at King's Cross, Clapham and Lockerbie sounded his death knell as a top politician.

Three years after his return to the backbenches in 1989, he made a half-hearted attempt to become the fourth member of his family to become Speaker of the Commons, a move foiled by the Commons' curious voting system, which favoured Betty Boothroyd. Instead, he served out his time as an effective chairman of the transport select committee, though by 1995 he had decided not to stand again for parliament. John Major made him a peer in 1997.

Channon is survived by his wife Ingrid, previously married to his cousin, Jonathan Guinness, now the 3rd Baron Moyne, their son Henry and his younger daughter, Georgia.

John Biffen writes:

By the time I arrived in the Commons in 1961, Paul Channon was already established as successor to his father in the Southend West constituency. He was an amiable and charming parliamentary companion, on the whole to the left of the Conservative party, and so a natural supporter of Edward Heath. Our policy differences never impinged on our personal friendship. He was a gentle controversialist, and in his ministerial career had the challenge of being opposed by such a sharp parliamentarian as the late Robin Cook (obituary, August 8 2005).

Though his ministerial duties were not particularly enjoyable, he bore them with good nature, and he never enjoyed hostilities. Great sadness struck him soon after leaving the Commons, such that he was unable to demonstrate his measured approach to politics as an active member of the Lords.